Great first impression - lovely atmospheric music and funny "blah blah" dialogue sound from the celestial octopus, I'm already delighted!
Beautiful and unique art style - there's a lot of polish and creativity on display here!
My constructive critique is that having the camera continuously drift downwards felt a little constricting at first (until I made peace with it), especially since it "feels" like my upward swim is strong enough to counteract the downward drift. It's a good gameplay element - forcing me to catch fish on time before they're off screen - but needs a stronger in-game justification. Maybe the player character has a visible diving weight attached and the upward velocity could be reduced - you could even allow the camera to go up a little bit before being counteracted by the downward force, if that makes sense...
I could definitely see myself playing this for longer, you can't go wrong with an upgrade progression loop like this set in a beautiful world.
Amazing job, team!